1. Field of the Invention
This invention relates to devices used to visually monitor the areas alongside and behind a motor vehicle while the vehicle is in operation.
2. Description of the Prior Art
It is necessary for a person operating a motor vehicle to be aware of other vehicles or other objects beside or behind his vehicle. Currently this is done through the use of rear view mirrors. Usually there is a rear view mirror inside the vehicle, centered high on the windshield to visualize the road behind the vehicle through the rear window. In addition, there is usually a mirror outside the door window on each side, to visualize the area beside and behind the vehicle.
Said rear view mirrors have several shortcomings. Firstly they each have a narrow field of vision so that they leave blind spots, particularly to the left rear and to the right rear of the vehicle. Such blindspots make it necessary for the driver to turn his head rearwards before he can change lanes or make appropriate maneuvers, thus diverting his attention from the area ahead of the vehicle. Features such as the roof-supporting pillars of the vehicle, head rests, and even passengers obstruct the view, so that even when the driver turns his head backwards, he still may not have a complete view of areas in the blind spots. Such obstructions are worse in delivery vans, trucks and buses.
The problems with the blind spots are especially severe with big trucks with “cab over engine” design where the outside rear view mirrors are necessarily placed at a high position, causing the driver to be unable to see low-silhouette vehicles alongside his vehicle. A system that will provide a rear view from a lower vantage point would go far towards solving this problem.
Yet another problem with outside rear view mirrors is that deposits of ice, snow or condensed moisture on the window adjacent to the mirror will obscure the driver's view of the mirror. Sometimes the exterior mirrors themselves become covered with occluding deposits such as condensed moisture, snow rain or dirt, thereby diminishing their effectiveness.
Because current outside rear view mirrors protrude outwardly from the otherwise smooth contour of the external surface of the vehicle, they detract from the vehicle's appearance and streamlined efficiency. It is not possible to reduce the size of this protuberance as long as its function relies on the use of mirrors which must necessarily be of adequate size.
There is also no way to adjust the brightness or contrast of the image seen in conventional rear view mirrors. What it reflects is what the driver sees, whether it is too dark or too glaring.
Currently some vehicles, especially towing trucks, are equipped with special video monitoring devices to visualize the towing hitch to assist the operator in maneuvering the vehicle for hitching it to the trailer. These video monitors are not, however, satisfactory for supplanting or complementing the rear view mirrors and do not solve the problems enumerated above. For one thing, a video camera facing backwards gives a regular direct view of the observed area, whereas a standard rear view mirror provides a “mirror image” of the observed area.
This difference is crucially important from the functional point of view because objects seen on one side of the mirror (when viewed through a standard rear view mirror) will appear on the opposite side of the viewing screen when seen through a rearward facing video monitor lens. The average driver, trained to react quickly to the mirror images presented by the standard rear view mirrors, will then tend to react with the wrong maneuver upon seeing these “turned around” direct images on the video screen. A better approach would be a system which would show a “mirror image” on the video screen just like the ones shown by the standard rear view mirrors. A driver could then use this system just as easily as he uses standard rear view mirrors. Furthermore, he would enjoy other advantages as discussed below.
In motor vehicles, whether automobiles or trucks, the driver's seat is positioned adjacent either the left or right side door and associated window. For example, in the United States the driver is adjacent the left door, and in England and other countries, the driver sits adjacent the right door. Accordingly, the driver is never seated equidistantly between the rear view side mirrors located outside the vehicle and adjacent the windows of the doors. As a consequence of the uneven spacing between the driver's head and the left or right side mirror, the driver's viewing angle is greater with respect to the closest mirror than the more distant mirror.
In order to cause the more distant mirror to provide the same effective field of view as the closer mirror, the more distant mirror is caused to have an outwardly convex curvature, which widens its viewing angle. However, the widened viewing angle causes objects seen in the mirror to appear smaller than they should be. This creates the psychological impression that such objects are further away than they really are, particularly in comparison with the image in the closer mirror, and such distorted impression can produce driving accidents. In fact, all such convex mirrors bear the message “Objects in mirror are closer than they appear.”
In a related issue concerning the location of the driver's eyes relative to the rear view mirrors, it is to be noted that, when drivers of different heights drive the same vehicle on different occasions, the angular position of all three mirrors must be adjusted. Although this is merely an inconvenience prior to travel in the vehicle, there could be serious consequences if such mirror re-adjustment is forgotten.
U.S. Pat. No. 4,277,804 to Robison discloses the use of a mirror in association with a television camera to provide a mirror image view of the area behind a trailer truck. The mirror image is viewable on a screen adjacent the driver of the truck. Robinson's system cannot be readily adapted to monitor areas at the sides of the truck.
U.S. Pat. No. 6,424,273 to Gutta et. al. discloses a vision system for an automobile employing paired television cameras protruding from opposite sides of the automobile forwardly of the driver, and a rearwardly directed third camera. The images provided by the cameras are displayed as a composite image in a single image display device located in front of the driver. This sytem would tend to be confusing to the average driver who would, by force of habit, automatically look to the direction of the left and right outside rear view mirrors to check the traffic situation in the left and right adjacent lanes.
It is accordingly an object of the present invention to provide a rear view monitoring system for use in motor vehicles for achieving improved observation of areas alongside and behind the vehicle, including areas generally referred to as “blind spots.”
A further object of this invention is to provide a monitoring system as in the foregoing object which provides a display of equal sized mirror images of observed areas on both sides of the vehicle.
An additional object of this invention is to provide a monitoring system that will, firstly, provide an image of the areas to the right and rear of the vehicle on a viewing screen located at or near the place where the conventional right rear view mirror is usually located; secondly, that will provide an image of the areas behind and to the left of the vehicle on a viewing screen located at or near the place where the conventional left rear view mirror is usually located; and, thirdly, that will provide an image of the areas directly behind the vehicle on a viewing screen located behind the upper middle portion of the windshield where the conventional inside rear view mirror is usually located, so that the ordinary driver will not need to change his regular viewing habits when checking for traffic in these corresponding areas.
It is another object of the present invention to provide a monitoring system of the aforesaid nature that is unaffected by occluding deposits on the vehicle's windows.
A still further object of this invention is to provide a monitoring system of the aforesaid nature which produces images that can be adjusted with respect to contrast and brightness.
Still another object of the present invention is to provide a rear view monitoring system whose components are substantially non-protrusive from the external surface of the vehicle, thereby enhancing the vehicle's appearance and streamlined contour.
These objects and other objects and advantages of the invention will be apparent from the following description.